Introduction:


In 1907 Leo Baekeland, a Belgian-American chemist, developed a new synthetic polymer with a combination of phenol and formaldehyde that he called Bakelite.  Since then, additional synthetic resins were developed that formed a basis for protective and decorative polymeric coatings.


Over the years, epoxies, polyurethanes, and polyureas formed the backbone technologies for high performance coatings.  Among these polymers, polyureas exhibited outstanding commercial acceptance compared with epoxies and urethanes, where an amine is made to react with a polyisocyanate to produce a fast-setting coating.  Polyureas have advantages as a coating system that includes rapid cure, high elongation, excellent abrasion resistance, and outstanding tear strength.  Polyureas generally lack the ability to resist color degradation upon exposure to UV.  The polyureas formed by the reaction of a polyaspartic amine with an aliphatic isocyanate maintain exceptional clarity and provide excellent resistance to fading upon exposure to sun and weathering, and these polyureas are called polyaspartics.


Polyaspartics have allowed us to achieve the following standards:


  • One-coat application – normally applied at 6-8 mils, but can be applied up to 16-18  mils, or more, in a single coat application;
  • Rapid curing compared with epoxies and urethanes --  resulting in a return-to-service in a few hours or the next day;
  • Weatherability – UV stable, color-fastness and non-yellowing compared with epoxies, along with high gloss and stain resistance;
  • Tough, Hard, Abrasion-Resistant Films – Scratch, abrasion and scruff resistance is greater than epoxies or urethanes;
  • Low VOC’s – Can be formulated for low viscosity at high solids or without solvents and with excellent flow and leveling in contrast to solvent-dependent epoxy and urethane coatings formulations where solvent odors restrict use;
  • Low-Temperature Applications – Can be applied at temperatures from -30°F up to 140°F;
  • Chemical Resistance and Good Mechanical Properties --  Enables a wide-variety of applications; and
  • Flexibility – Polyaspartics can now be formulated with extraordinary flexibility and strength, allowing for application on flexible substrates such as wood, plastics, and metal.


These characteristics make polyaspartic coatings ideal for concrete flooring applications as well as many other applications, including:


  • Concrete Resurfacing
  • Direct-to-Metal
  • Wood Coatings
  • Plastics Coatings
  • Wind Turbines
  • Hybrid Technologies
  • Composites
  • Gel Coats
  • Patching Compounds, Joint and Crack Fillers and Putties
  • Concrete Decking



Chemistry of Polyaspartics:


Aspartics are prepared by Michael addition of di-amines onto maleic acid which are secondary aliphatic di-amines. Steric hindrance is built into the molecule via the di-amine, which has a significant advantage over conventional polyamines, the use of which is limited by extremely high reactivity with low-cost aromatic polyisocyanates. Thus, polyaspartics make up a special class of hindered secondary amines whose reactivity is custom-designed for desired performance using conventional application methods.


Compared to the typical secondary amines, polyaspartic chemistry allows coatings to be formulated with sufficient pot life as well as low viscosity to allow the use of a brush or roller.  In addition, faster return-to-service has enabled polyaspartic coatings to save time and money for the applicator.


Compared to the traditional polyurethane chemistry, the reactivity between the amine and the aliphatic polyisocyanate in polyaspartic chemistry enables the formulator to forgo using a tin catalyst, and this allows the polyaspartic coating to be applied at higher film thicknesses than the traditional polyurethane coatings. This minimizes bubble formation and bubble release caused by the carbon dioxide gas produced by tin when it catalyzes the isocyanate reaction with water.  Bubbles and foam are especially present when polyurethane coatings catalyzed with tin are applied at higher levels of humidity.




Applications:


In 2016 a new technology for polyaspartics was introduced to the industry by Pflaumer Brothers, Inc., consisting of new, low viscosity trimer polyisocyanates developed especially to extend the working time of 2-K polyaspartics.   Continuous research by Pflaumer focused on innovative chemistries to develop a new polyaspartic amine, commercialized in 2018, used by itself or as a modifier to extend working time in combination with conventional trimer polyisocyanates. Polyaspartic polyurea overcomes many of the practical complexities of a polyurea, while retaining the finest properties of both polyurea and aliphatic urethane. Polyaspartic is a type of polyurea (actually a polyaspartic aliphatic polyurea) where the –NCO terminated pre-polymer is reacted with secondary or hindered aliphatic di-amines, resulting in polyurea linkages, but giving ample time (20-30 minutes) for application by conventional methods like brushing or rolling.


Pflaumer also introduced new functional additives during this period  to improve flow and leveling along with bubble release, thus improving overall appearance with brush and roller applications.  Reactive and non-reactive diluents were added in 2018, replacing conventional solvents and enabling the formulation of high solids polyaspartics at low viscosities. Colorants specifically developed for polyaspartics by Pflaumer were introduced that enabled the formulator to offer special designs both indoors and outdoors to their clients. Thus, by 2020, the coatings chemist was able to formulate polyaspartics with working time, color, appearance, performance, and application properties approaching that of epoxies and urethanes – but with a system capable of one-coat application and a quick return-to-service. 


Polyaspartics have a relatively low viscosity compared with conventional polyureas, and they  provide  good wetting ability onto properly prepared concrete and can be applied at  higher dry-film thickness in a single coat, apart from UV stability and excellent chemical and abrasion resistance. Polyaspartics  can be applied at a wide range of temperatures, bonds easily to concrete surfaces, and cures to touch within an hour or so. It can be formulated to be flexible enough to bridge small cracks, and can withstand relatively higher temperatures when cured, and impart bubble-free, high gloss films.


The stunning advantage of polyaspartic chemistry is its fast cure which means that there is virtually no down time and one thick layer can be applied in a single application in a single day. The coating is easily applied at room temperature, requires no external heat source for curing, and the surface can be walked on after just a few hours.